new Mac systems that have SSD boot drives will format with the new Apple APFS file format, not HFS+.
If your drive is formatted with AFPS, this cannot be read on an Mac with an older operating system.
https://en.wikipedia.org/wiki/Apple_File_System
https://support.apple.com/en-us/ht208033
from the above doc -
•APFS requires macOS High Sierra. Earlier versions of the Mac operating system don't mount APFS-formatted volumes.
Bob Zelin
Bob Zelin
Rescue 1, Inc.
bobzelin@icloud.com
